2. DoubleClick

Price: $3.1 billion

Announced: April 2007

FTC Approval: December 2007 (March 2008 in Europe)

    Of the big three, DoubleClick will be the most obscure name for the layman reader. But it shouldn't be, given the huge role DoubleClick's display ad business plays for Google. Regulators knew that, which led to protracted investigation, especially in Europe. Once given the green light, Google made DoubleClick its core business for display ads, what analysts had considered a weakness for the company. Reports from the time noted the steep price tag but applauded Google for taking steps to catch up with Yahoo! and Microsoft in such ads. DoubleClick was the first, and biggest, of Google's major advertising capability buys -- what CitiGroup called Google's "very expensive but very significant strategic thrust."

1.Motorola Mobility

Price: $12.5 billion

Announced: August 2011

FTC Approval: TBD

    The crown jewel of Google's acquisitions -- but for its patents, not its "Hello Moto" ads. This monster deal will convert Google from smartphone OS provider to smartphone maker, which may make some of its other partners nervous. Companies like HTC and Samsung, however, have expressed satisfaction in the deal for its investment in the protection of Android from legal attacks by rivals such as Apple and Research in Motion.

    The key is Motorola's patent treasure trove of 17,000 patents and 7,500 awaiting approval. Google's struggle to protect itself is not new, and after its failure to buy Nortel's patent cache earlier this year, this move represents a stunning counterattack. In its note following the announcement today, Nomura wrote to investors that it expected the patent crisis for Google to now subside. The main concern -- besides the big-money price tag? CitiGroup's note warned that, given past regulatory delays, the deal may not close before 2012.